The present disclosure is directed to a turbine engine component having a platform with a cooling circuit and a process for forming same.
Currently, a high level of cooling technology for turbine airfoil platforms involves the placement of a miniature core within the wall of the platform. This core is suspended between the hot side of the wall, or gas path, and the cold side of the wall. This technology pulls air from the cold non-gas path side through a number of cooling fins, i.e. trip strips protruding from the gas path side, and pins or pedestals spanning between the hot and cold walls. The air is evacuated out onto the gas path surface where the air spreads out on the surface to create a thin film of cooler air to help further protect the surface from hot gas path air.
FIG. 1 illustrates a turbine vane 10 with a platform cavity 12 which has been formed using a core 14 (see FIG. 2). The vane has outer 16 and inner 18 platforms, with an airfoil 20 spanning there between. The airfoil 20 has multiple internal cavities 22 and 24 and has a pressure or concave side 26 and a suction or convex side 28. The outer and inner platforms 16 and 18 respectively both have a hot gas path side 30 and a cooler non-gas path side 32. The outer platform 16 has a platform cavity 12 whose entrance 34 allows the cooler air on the non-gas path side 32 to enter the cavity 12 and flow through the cavity 12 to exit onto the hot gas path side 30 of the outer platform 16 where this air creates a thin film of cooler air on the surface which protects that surface from the hot gas path air.
FIG. 2 shows a cut away of the outer platform 16 prior to the cores 36 and 38 which form the airfoil cavities 22 and 24 being leached out. Also shown in the figure is the core 14, prior to it being leached out. The core 14 has holes 40 of varying shape in it that helps create turbulent air flow within the cavity and increase surface area thereby increasing the heat transfer capability of the air.
FIG. 3 shows a cut away of the outer platform 16 after the cores 36 ad 38 have been leached out of the airfoil to form the airfoil cavities 22 and 24. The figure also shows the cavity 12 which is formed by the core 14 after it has been leached out. When the platform core 14 is leached out, the holes 40 in the core 14 leave a three dimensional mirror solid behind in the form of a plurality of pedestals 42. Also trenches in the core 14 create trip strips 44 to further increase the turbulence of the air and increase the surface area, thereby increasing heat transfer.
FIG. 4 shows a close up of the cut away of the cavity 12 in the outer platform 16 and shows the arduous paths 46 the air must travel from the entrance 34 of the cavity to the exit 48 on the gas path side of the platform.
This technology works extraordinarily well; however, it is complicated to implement in turbine vanes. It requires a four piece wax assembly for a turbine doublet which is not production friendly. The technology is expensive.